St. Croix Success: Zebra Mussels on Decline in River's Waters

One of the most dreaded invasive species, zebra mussels, are on a nationally recognized steep decline on the St. Croix River, to the point where a 2011 report states the abrasive creatures are all but gone. 

The good news? Last year's counts didn't ring any alarm bells that the mussels were on the way back. That's good news just weeks before boaters hit the water for fishing season and other recreation activities. 

The 2011 report, filed by the National Park Service and handed over to the United States Corps of Engineers about a year ago, states the search for fingernail-sized mussels, which have spread rampantly through lakes across Minnesota, came up empty in the river's deep basin, known as Lake St. Croix.

The report shows that the zebra mussels, found in the river right around the turn of the century, was previously found in nesting beds at eight regular testing sites up and down the river's last 21 miles. 

Recent searches, however, showed the mussels on steep decline in spots near Stillwater's harbor, Hudson, and points beyond until the river meets with the Mississippi near Hastings. 

The Minneapolis Star Tribune reported the mussels might have been wiped away by high water in both 2010 and 2011. Or, common carp may have feasted on the little mussels. 

Drastic changes in populations might also just naturally occur, experts said, and by no means shold the invasive species be deemed "eradicated." 

Byron Karns, the National Wildlife Service biologist who prepared the 2011 report, said the low numbers shouldn't be taken as a sign the zebra mussels are gone. However, he told the Star Tribune last year, anything that shows numbers dropping should be taken as "good news."